This invention relates generally to a new and improved thermoelectric heat pump and more particularly relates to an improved thermoelectric heat pump of the type generally disclosed in U.S. Pat. No. 4,007,061, patented Feb. 8, 1977, entitled THERMOELECTRIC HEAT PUMP, Georges LeCouturier inventor, and U.S. Pat. No. 4,855,810, patented Aug. 8, 1989, entitled THERMOELECTRIC HEAT PUMP, Allan S. Gelb et al. inventors, and more particularly to an improvement of the thermoelectric heat pump disclosed in the second identified patent.
A typical simple thermoelectric heat pump is illustrated diagrammatically in FIG. 1 and is identified by general numerical designation 10. Heat pump 10 is for transferring heat from the body to be cooled, or heat source, 12 to a heat sink 14 and includes a pair of n-type and p-type semiconductors 15 and 16 having their upper ends connected to a copper conductor or bus 17 and having their opposed lower ends connected respectively to copper conductors or busses 18 and 19 either directly by soldering or indirectly by being soldered to nickel/tin plating provided on the conductors 18 and 19 as known to the art. The copper conductors 17 and 18 and 19 are connected by low temperature solder as known to the art, respectively to the electrical insulation members 20 and 21, which are also good heat conductors and which may be for example ceramic. The insulation members 20 and 21 are connected respectively to the body to be cooled 12 and the heat sink 14 by mechanical bolting, thermal glue or low temperature solder. An electrical circuit, including a dc source 22, is connected between the electrical conductors or busses 17 and 18 and 19. Heat from the body to be cooled 12 is pumped thermoelectrically to the heat sink 14 at a rate proportional to current passing through the circuit and the number of pairs of n-type and p-type semiconductors included in the heat pump 10. The opposed ends of the n-type and p-type semiconductors 15 and 16 are typically connected or adhered to the copper conductors or busses 17 and 18 and 19 by relatively low temperature solder having a melting point of about 86.degree. C. The reason that such low melting point solder is used is that it is such low melting point solder that can be used to adhere to both the n-type and p-type semiconductors 15 and 16 to the copper conductors or busses 17 and 18 and 19 and to adhere such busses to the insulation members 20 and 21.
As is further known to those skilled in the art, the higher the temperature at which the thermoelectric heat pump can operate, the greater the amount of heat that can be pumped thermoelectrically from the body to be cooled to the heat sink, but the higher the temperature at which the thermoelectric heat pump operates the greater the heat present and such greater heat can undesirably melt the solder connection between the semiconductors and the copper busses thereby deteriorating and ultimately ruining the operation of the thermoelectric heat pump. More particularly, use of the above-noted relatively low temperature solder having a melting point of about 86.degree. C. practically restricts the operating temperature of the heat pump to a temperature below such solder melting point typically, as indicated by good practice as known to the art, about 25.degree. C. below the melting point of the solder. Accordingly, there exists a need in the thermoelectric heat pump art for a heat pump that can use relatively high temperature solder having a melting point of at least about 220.degree. C. to about 330.degree. C. so as to increase the temperature at which the heat pump can operate thereby increasing its efficiency and rate at which it can thermoelectrically pump heat.
As is further known to those skilled in the art, a further problem with thermoelectric heat pumps of the type illustrated diagrammatically in FIG. 1 is that the solder used to connect or adhere the opposed ends of the semiconductors 15 and 16 to the copper busses 17 and 18 and 19 typically includes a metal component which, as is further known, tends to migrate or diffuse into the semiconductors during prolonged operation of the heat pump which increases the conductivity of the semiconductors and decreases their semi-conductivity which is deleterious to their operation and which ultimately can be ruinous; metal also tends to migrate or diffuse into the semiconductors from the electrical conductors or busses 17 and 18 and 19 causing the same problem. A solution to this metal or metal diffusion or migration problem is disclosed in U.S. Pat. No. 4,855,810 identified above, and such solution is the inclusion of coatings or plated layers of nickel 16 and 18, shown in FIG. 1 of this patent and which plated layers of nickel are taught as being metal or metallic diffusion barrier plates, coatings or layers. Such layers of nickel are plated onto the opposed ends of the semiconductors, but as is further known to the art nickel does not plate and adhere to semiconductor material as well as is desired. This presents another problem as known to those skilled in the art, because the semiconductors are made in large sheets or layers of semiconductor material, the nickel plated thereon, after which the discrete or individual n-type and p-type conductors are produced by cutting the large layers of nickel plated semiconductor material into such discrete semiconductors. The cutting of the large layers of nickel plated semiconductors into discrete plated n-type and p-type semiconductors has the known problem of the plated nickel tending to delaminate during the cutting process. Accordingly, there exists a further need in the art for enhanced adherence of such layers or platings of nickel to the opposed ends of the semiconductors.